Image-forming devices well known in the art have been constructed of a sheet metal frame and a resin frame for supporting and positioning various components, including a paper cassette, a belt for conveying paper, a process unit including a photosensitive drum and a developing device, a scanning unit for exposing the photosensitive drum, a transferring unit, a fixing unit, and a discharge device for discharging paper. An example of such an image-forming device is disclosed in Japanese unexamined patent application publication No. 2001-77548.
Use of the resin frame described above increases the level of freedom in designing the image-forming device since the resin can easily be molded into complex shapes. Consequently, a more compact image-forming device can be produced by arranging the components efficiently. However, since resin frames have low stiffness, mounting a sheet metal frame having high stiffness on the resin frame can reinforce the resin frame and improve the positioning precision of the components. In this way, it is possible both to reduce the size of the image-forming device and to improve positioning precision of the components therein.